This invention relates to a thermally releasable flavor source for use in smoking articles which produce substantially no smoke. More particularly, this invention relates to a tobacco-containing thermally releasable flavor source that provides the sensations associated with the smoking of tobacco without the burning of tobacco.
A substantial number of previous attempts have been made to produce a smoking article which produces an aerosol or vapor for inhalation, rather than smoke. For example, Siegel U.S. Pat. No. 2,907,686 shows a smoking article consisting of a charcoal rod and a separate carrier impregnated with flavorants and a synthetic "smoke" forming agent which is heated and volatized by the burning charcoal rod. The charcoal rod is coated with a concentrated sugar solution so as to form an impervious layer during burning. It was thought that this layer would contain the gases formed during smoking and concentrate the heat thus formed, thereby thermally releasing the flavorants.
Another smoking article, shown in Ellis et al. U.S. Pat. No. 3,258,015, employs burning tobacco in the form of a conventional cigarette to heat a metallic cylinder containing a source of nicotine, such as reconstituted tobacco or tobacco extract. During smoking, the vapors released from the material inside the metal tube mix with air inhaled through an open end of the tube which runs to the burning end of the smoking article. Ellis et al. U.S. Pat. No. 3,356,094 shows a similar smoking article in which the tube becomes frangible upon heating, so that it will break off and not protrude as the surrounding tobacco burns away.
European patent application 0 177 355 by Hearn et al. shows a smoking article which produces a nicotine-containing aerosol by heating, but not burning, a flavor generator. The flavor generator could be fabricated from a substrate material such as almumina, natural clays and the like, or tobacco filler. The flavor generator is impregnated with thermally releasable flavorants, including nicotine, glycerol, menthol and the like. Heating of the flavor generator is provided by hot gases formed as a result of the combustion of a fuel rod of pyrolized tobacco or other carbonaceous material.
Banerjee et al. U.S. Pat. No. 4,714,082 shows a variation of the Hearn et al. device which employs a short fuel element. The performance of the device is improved by maximizing heat transfer between the fuel element and the aerosol generator. This is effected by preventing heat loss by insulation, and by enhancing heat transfer between the burning fuel and the flavor generator by a metallic conductor. A spun glass fiber insulator surrounds the fuel element and aerosol generator assembly.
European Application No. 0 212 234 shows a smoking article having an aerosol generating means abutting a fuel element. The aerosol generating means is said to include a thermally stable, porous particulate substrate material, for example, carbon, tobacco, or mixtures of carbon and tobacco formed into densified spherical particles in a one step process (e.g., as described in U.S. Pat. No. Re 27,214) in a "Marumerizer" type machine. The substrate materials carry one or more aerosol forming materials and may include one or more volatile flavoring agents. The smoking article may include optionally a plug of tobacco at the mouth end of the fuel element whereby hot gases passing through the tobacco may vaporize volatile components in the tobacco without combustion.
European Application 0 254 848 shows a substrate material having a decreased retentive capacity for use as a carrier for aerosol materials, e.g., alumina or modified carbon.
The prior art devices that rely on thermally releasable flavorants have not heretofore adequately provided a flavor source for smoking articles that will provide the smoker with the taste and satisfaction that has become expected of a conventional tobacco-burning smoking article. Accordingly, there is a continuing need for a flavor source that can be heated to provide an acceptable taste comparable to a conventional smoking article without being burned. Further, there is a continuing need to provide such a flavor source containing tobacco.